Method of manufacturing optical device

Abstract

In a method of molding an optical device by press-molding a glass preform by using molding dies, the press-molding process is executed under a mixed gas atmosphere of a nonoxidizer gas and a hydrocarbon gas.

What is claimed is: 
     
       1. A manufacturing method of molding an optical device having an accurate optical surface, comprising the steps of: preparing a glass preform;   preparing a die member to mold said glass preform into said optical device,   said die member having at least an upper die and a lower die for molding said optical surface in order to press-mold the glass preform, and said die member being made of a material resistant to oxidation, and high temperature and having a high hardness property;   individually heating said glass preform and said die member to a temperature necessary to mold;   inserting said glass preform between said upper die and said lower die; and   press-molding said glass preform between said upper die and said lower die in an operating atmosphere of a gaseous mixture of a nonoxidizing gas and a hydrocarbon gas, said hydrocarbon gas being present in a concentration of 0.5-4 wt. % of said gaseous mixture.   
     
     
       2. A method according to claim 1, wherein said die member is made of a tungsten carbide material. 
     
     
       3. A method according to claim 2, wherein a film made of a material of selected from the group consisting of a nitride, a carbide, and an oxide is coated onto the surface of the die member which comes into contact with the glass preform. 
     
     
       4. A method according to claim 1, further comprising the steps of: adhering said gaseous mixture to said glass preform surface and press-molding;   inserting said glass preform between said upper and lower dies.   
     
     
       5. A manufacturing method of molding an optical device having an accurate optical surface, comprising the sequential steps of: preparing a pre-molded glass preform;   preparing a die member to mold said glass preform into the optical device;   transporting said glass preform and said die member to a heating section and heating to a temperature necessary to mold,   adhering a gaseous mixture of a nonoxidizing gas and a hydrocarbon gas onto the surface of said glass preform, said hydrocarbon gas being present in a concentration 0.5-4 wt. % of said gaseous mixture.   transporting said glass preform and said die member to a pressing section for press-molding said glass preform into an optical device; and   transporting said die member and said optical device to a cooling section for cooling said optical device to a temperature sufficient to separate said mold member from said optical device.   
     
     
       6. A method according to claim 5, wherein said die member is made of a tungsten carbide material. 
     
     
       7. A method according to claim 6, wherein a film made of a material selected from the group consisting of a nitride, a carbide, and an oxide is coated onto the surface of the die member. 
     
     
       8. A manufacturing method of molding an optical device having an accurate optical surface, comprising the steps of: preparing a pre-molded glass preform;   preparing a die member to mold said glass preform into said optical device,   said die member having at least an upper die and a lower die for molding said optical surface in order to press-mold said glass preform, and said die member being made of a material resistant to oxidation and high temperature, and having a high hardness property;   simultaneously heating said glass preform and said die member to a temperature necessary to mold;   inserting said glass preform between said upper die and said lower die; and   press-molding said glass preform between said upper die and said lower die in an operating atmosphere of a PG,41 gaseous mixture of a nonoxidizing gas and a hydrocarbon gas, said hydrocarbon gas being present in a concentration of 0.5 to 4 wt. % of said gaseous mixture.   
     
     
       9. A method according to claim 1, including employing a ceramics sintered material die member. 
     
     
       10. A method according to claim 5, including employing a ceramics sintered material die member. 
     
     
       11. A method according to claim 1, including employing a PbO-containing glass preform. 
     
     
       12. A method according to claim 5, including employing a PbO-containing glass preform.